Aromatics Extraction. 1. Extraction Characteristics of ILs for the Toluene/Heptane Separation and Equipment Design Aspects

Abstract

The study focuses on the separation of aromatic hydrocarbons from aliphatic hydrocarbon mixtures in the presence of new extraction solvents – ionic liquids (ILs). A comparison of various solvents suitable for liquid-liquid extraction of aromatic - aliphatic hydrocarbon mixture is presented. Toluene and heptane were chosen as the representatives of the aromatic and aliphatic hydrocarbon families. As extraction solvents, ILs such as 1-ethyl-3-methylimidazolium ethylsulfate ([EMim][ESO4]), 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([EMim][NTf2]), 3-methyl-N-butylpyridinium tetracyanoborate ([3- mebupy][B(CN)4)], and 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([EMpy][NTf2]) were selected. Selection of ILs from the potential candidates was based on the toluene/heptane selectivity and toluene distribution coefficients in heptane–toluene–IL mixtures published in literature. The effect of extraction properties of the selected IL solvents on the hydrocarbons mixture separation is documented by the results of the counter-current extractor simulation. For a comparison of the selected IL solvents basic extractor design parameters such as the number of theoretical stages, solvent to feed mass ratio, and the purity of the product were determined. The results were compared to those obtained for sulfolane, an extraction solvent considered as a benchmark for the aromatic–aliphatic hydrocarbons mixtures separation. For the thermodynamic description of LLE, the NRTL equation was used.